A pet’s body is home to a plethora of bacteria and yeast, both inside and out. These organisms make up what we call the “normal flora” and they protect our pets from disease, help digest their food, and boost their immune systems.

But sometimes, the numbers of normal flora get out of whack and lead to trouble. This is the case when we have pets with yeast infections. Yeast are commonly found in low numbers in the ear canal, on the feet, and on the skin of our pets, but when the number of yeast organisms grow abnormally high, infection is the result.

Yeast (or Malassezia) infections of the ear and skin, also commonly called Malassezia otitis externa and Malassezia dermatitis, respectively, are common in dogs. They can occur in cats, as well, but our canine friends are by far more commonly affected. When yeast overgrowths occur, smelly skin and ear infections will be the result.

Causes of yeast infections

Sometimes immune deficiencies allow the yeast to overpopulate, and sometimes an excess production of oil or a persistent bacterial skin infection is to blame. Hypothyroidism and atopy are other leading causes of yeast infections in dogs. Finally, environmental factors, such as heat and increased humidity, also play a role.

A dog of any age or sex can develop an overgrowth of yeast in their ear or on their skin. The condition is so common that I think I’ve seen it in almost every breed (or mix), but some unfortunate souls are more prone than others, including:

  • West Highland White Terriers
  • Basset Hounds
  • Cocker Spaniels
  • Labrador Retrievers
  • Dachshunds

Signs and symptoms

Pets with Malassezia infections are itchy. If the infection is in their ears, they scratch their ears. If the infection is between their toes, they lick and chew their feet. If the infection is on their muzzles, they’ll rub their faces along the floor, couch, or your lap. You get the picture – these poor dogs (and cats) are miserable with itch. And they stink. Pets with a yeast overgrowth will have a yeasty smell, quite fittingly.

Yeast dermatitis (skin infection) will present as a greasy, waxy coat along with crusting lesions. In chronic cases, hair loss and increased skin pigment are often seen. Skin infections often go hand in hand (or should I say paw in paw) with yeast overgrowths in the ears.

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Diagnosis is relatively simple. Your vet will take a sample from your pet’s ear (using a cotton swab) or skin (often using a piece of Scotch tape) and look for the yeast organisms under the microscope. If a yeast infection is to blame for your pet’s symptoms, the evidence will be abundant under the microscope.


Treatment will almost always include a topical medication, such as ear drops or medicated shampoo. Sometimes oral medications are required as well. Yeast overgrowths are usually easy to control, but will recur unless the underlying cause is addressed. Pets with allergies and oily seborrhea will always be prone to yeast overgrowths, so pet owners should stay vigilant to nip them in the bud!

Dec 12, 2013
Pet Health

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